According to the increase in speed and integration of semiconductor devices, there has been an increasing demand for a multilayer wiring structure which is capable of increasing the number of wiring layers and miniaturizing wiring patterns. Thus, the multilayer wiring technology is an important issue for a sub-micron process.
In particular, as a process margin for a depth of focus in an exposure device for forming a micro pattern shrinks with the age of sub-0.35 μm process, a global planarization technology for a chip area is required in order to secure a sufficient depth of focus.
Thus, in order to realize global planarization, a technology referred to as CMP is widely used. The CMP technology is necessarily applied to a method for fabricating a semiconductor device, and research is being actively conducted on next-generation elements. According to the recent trend, the CMP technology has been frequently applied to logic elements which require a multilayer wiring in order to increase the operation speed of the elements. Furthermore, the application of the CMP technology has gradually widened as more and more memory elements have a multilayer structure.
Furthermore, a CMP apparatus based on the CMP technology may include a retainer ring which is installed on a polishing head for fixing a wafer so as to perform a mechanical operation. The retainer ring is used to fix the regular position of a held wafer.
However, since the retainer ring is formed of a resin material such as plastic, the strength of the retainer ring is low. Furthermore, a planarization operation for the retainer ring, which is performed before a CMP process, requires a large amount of time, and uneven wear may occur due to an imbalance of force caused by cover bolt tightening.
Thus, a retainer ring structure including an inner ring and an outer ring is widely used. The inner ring serving as an insert ring is formed of a metallic material, and the outer ring covering the insert ring is formed of a resin material such as plastic.
The above-described retainer ring structure including an inner ring and an outer ring has been disclosed in a method for manufacturing a ring structure, which was applied and registered on Jun. 9, 2010 and titled “Method for manufacturing retainer ring of mechanical polishing apparatus”, and a method for manufacturing a ring structure, which was applied and registered on Aug. 18, 2010 and titled “Retainer ring structure for CMP apparatus and method for manufacturing the same”.
However, according to the method for manufacturing a retainer ring, a part to which a fastening screw mounted on a polishing head is fastened is formed of a resin material. Thus, the fastening screw inevitably has a small fastening force, and local deformation may occur when the fastening screw is coupled.
Furthermore, after the metallic inner ring is formed, an insert pin having a head formed thereon is coupled to a hole formed at the top surface of the inner ring. Then, a resin material is injected to mold a ring structure.
After the ring structure is cooled, the head of the insert pin is cut, and a hole or screw thread is formed in the body of the insert pin. Then, the retainer ring structure is completed. As described above, the method for manufacturing a retainer ring includes complex and many process steps. Thus, the manufacturing cost inevitably increases, and the manufacturing operation accompanies many difficulties.